It has become increasingly recognized that low vitamin D levels are prevalent worldwide and to a more severe degree in the Middle East. Low vitamin D levels are associated with an increased risk of osteoporotic fractures, and of chronic conditions such as autoimmune disorders, diabetes, cancer, and the metabolic syndrome. Obese individuals are more likely to have low vitamin D levels, and in some studies obesity was a risk factor for fractures in both the young and elderly. Our group has investigated the impact of vitamin D therapy in the young, and preliminary data suggest that doses exceeding the currently updated recommended estimated average requirement (EAR) of 400IU for that age group may be more beneficial for bone health. The updated EAR recommendations by the IOM for any age group, although believed to cover the needs of all individuals in each age group, are limited by the lack of good evidence supporting such recommendations. Therefore, to-date, the optimal dose of vitamin D for both the young and elderly is unknown.